When designing HMI/SCADA, consider many factors

When designing hardware and software for human-machine interface (HMI) and supervisory control and data acquisition (SCADA), there’s a lot more to it than just the basics. Understanding the core principles and pertinent standards are crucial, but there are many related factors that should also be considered. These include a company’s standards, user abilities, skill levels, process needs, future plans and integration with other systems. If a company’s planning involves looking at the bigger picture, a finished product will be the better for it. Several best practices can help.

An important first step is to identify your own company’s standards. Industry or regulatory standards are important, but companies can realize benefits from having their own standards as well.

“Companies looking at improving their systems should think about identifying internal standards,” said Kent Melville, application engineering manager for Inductive Automation, maker of the Ignition industrial application platform. “If organizations take the time to define their own standards, they’ll ensure they’re using the protocols they really want to put in place, the type of hardware they want to put in place, and so on.”

Identifying your organization’s own internal standards is a good first step. Courtesy: Inductive Automation

Company standards for SCADA design

Having company standards makes it easier for an organization to stick to its plans and not be swayed into bad decisions. Melville said it can be difficult to maintain standards sometimes, because a lot of work gets done through vendors. Installing proprietary equipment and software can make it cost-prohibitive for companies to make changes later on. And because different proprietary systems don’t talk to each other, companies don’t always know how things will be affected if a change is needed.

“People really need to take ownership of their systems, and not let things be dictated by vendors,” said Melville. “To maintain your own standards for PLCs, protocols, data structures, and more, it often comes down to two options. One, you can pick a proprietary solution, where the manufacturer provides everything. Or you can work with companies that support open standards. With this open approach, even if you’re talking about different companies, all their products communicate with each other and work well together.”

Working with open standards provides a lot more control of the process. Courtesy: Inductive Automation

Integrator: Use smart SCADA, HMI standards

If working with a system integrator, clarifying standards up front will make the overall goals easier to understand. “We’ve seen the full spectrum of standards,” said Davin McDougall, business unit leader for Brock Solutions, an integrator that’s implemented projects around the world in a variety of industries. “We’ve seen no standards, poor standards — which can be worse than no standards — all the way up to world-class standards. When you get the standards right, we refer to them as ‘accelerators.’ Everyone wants to embrace and invest in accelerators, because they’ll help things go faster.”

McDougall described a project in which standards played a key role and greatly benefitted the customer. “Their operating model relies on the implementation of practical and effective standards throughout their organization,” he said. “Within the controls, for instance, you’ll find standard add-on instructions, user-defined data types, tag naming conventions, program structures, and a list of general setup parameters. They’ve standardized on hardware and infrastructure as well, albeit with a combination of vendors, for best in-class solutions. Within the SCADA domain, HMI templates, connectivity, screen headers/footers, general navigation, fonts, and font sizes are all standardized. So no matter where you are within the enterprise, a single-speed motor is controlled the same way, by the same code, and looks the same to the operator. And for the maintenance tech, troubleshooting a faulted single-speed motor is the same process anywhere in the enterprise.”

Consider the needs of all stakeholders before designing for HMI/SCADA. Courtesy: Inductive Automation

Process requirements for operators, integrators, supervisors, IT

When considering process needs, it’s important to look beyond the specific line or whatever else a project might be focused on. It’s best to see it holistically. “When putting controls in place, it’s really good to take a page out of IT’s book,” Melville said. “IT puts a lot of emphasis on requirements-gathering and making sure all stakeholders are involved. The stakeholders would include anyone affected by the project — operators, integrators, supervisors, the IT team that must support it, and C-level executives who want to see metrics. Everyone with a stake in the process should be involved in defining the requirements. However, you need to give the proper weight to each group’s input. For example, the operator who uses the system every day should have significant weight in the discussion.”

McDougall also sees great value in getting input from stakeholders. “I think it’s important to have stakeholder engagement throughout the project,” he said. “All stakeholders need to be involved when it comes to requirements-gathering, designing, building, testing, commissioning, and sustaining these projects. And ‘all stakeholders’ often includes engineering, IT, quality, maintenance, operations, finance, and partners like the systems integrator and technology vendors. As soon as you forget a stakeholder, the risk profile on the project goes up significantly.”

Different displays and sets of data should be provided to different groups of users. Courtesy: Inductive Automation

Abilities and skills for HMI and SCADA use

Questions to ask yourself also include: How will people interact with this system? And what’s their experience level?

“On the plant floor, it’s usually about the operator who’s seeing the system on a fixed screen, and they need the info quickly,” Melville said. “And it might be a guy who’s been doing this work for 20 years. That person’s going to need something that’s familiar. If the new system is too different from what he’s used to, he may not learn it properly, or he may become frustrated. You’re walking a fine line, because you want to use new technologies, but you don’t want things to be so different that they alienate people.”

Also, companies need to look at the variety of “user stories” within the organization. “For the operator who needs to quickly identify whether something is running within parameters or not, you’re probably wanting to use high-performance graphics,” Melville said. “With that approach, things running normally are in grayscale, and you’re using brighter colors for things that demand immediate attention, to show things that are out of spec. And you also have to think about the operator’s capabilities, and what the job allows him or her to do. In other words, how much time does he or she have to study these SCADA screens? That’s a factor that should be considered. For supervisors or C-level people on the business side, the user story is different. There, people aren’t necessarily limited to just a quick glance. They can take the time to analyze the data in some depth, so they can make decisions from the information. It can be more complex and have more detail than what the plant-floor operator might need. So every group is different, and if you only design things for one stakeholder, you won’t end up giving everyone what they need.”

Operators’ experience and skill levels should be factored into the equation. Courtesy: Inductive Automation

Mobile-responsive HMI, SCADA system integration

Melville also said companies may want to employ mobile-responsive design. For example, executives may want to see data on a mobile device. It’s harder to adapt a desktop design to a mobile device than it is to design for a mobile device first. If you need to design HMI for mobile, it’s best to know that in advance.

“And in general, when you’re looking at your user interface, you want things to be intuitive, and you want to be able to move fast,” Melville said. “Try to avoid using ‘tips,’ keyboard shortcuts, right-clicking on certain parts of the screen, and things like that. You don’t want hidden functionality. You want people to be able to learn it quickly. And if you use hidden functionality, it can become tribal knowledge, and new people aren’t going to know about it. And as people retire, the knowledge is lost.”

Think about how the system needs to be integrated with other systems. If the company is using open standards, integration is much easier. If you’re pushing data to the cloud, or doing a report for a government agency, you can do that because your data is centralized. You want a system where it all works together, and data can be shared. A big part of keeping things open is having real-time data. It’s really helpful to use modern tools and techniques, like application program interfaces (APIs,) OPC UA, and storing into an open database format that can be queried, for example.

The ability to easily access data will also help with the relationship between operational technology (OT) and information technology (IT). As IT sees modern scalable approaches to OT problems, it can be easier to get funding to maintain standards, because they see it benefits the entire organization. Companies can do more initiatives with IT involved. IT can be the champion, and get corporate budgets for projects, rather than working within constrained OT budgets.

Intuitive interfaces allow operators to absorb data and make decisions more quickly. Courtesy: Inductive Automation

Seven SCADA system integration/design questions to ask

As part of the discussion around integrating with other systems, you need to ask:

1. Who will need this data.
2. From where do they need to access it?
3. Are things read-only or read-write?
4. Do you need a demilitarized zone (DMZ) to enhance cybersecurity?
5. Are people using a virtual private network (VPN)?
6. Do you need to avoid sharing data externally because you’re in a regulated industry?
7. Is your mobile app something that can be used from anywhere, or can people only use it if they’re connected to the local Wi-Fi network at the plant?

Future plans: Review standards annually

When creating an organization’s standards, companies can’t expect them to be applicable in the same form 10 years from now. Technology changes rapidly, so companies need to evolve with those changes.

“It’s a good idea to establish a group of stakeholders that meet regularly to discuss standards,” Melville said. “The group should meet at least once a year to review its standards, and make changes as needed. And of course, changes can be costly, so your team needs to study needs and possibilities. Put some real thought into it to arrive at the best course of action. Picking technologies that will be supported long-term, will result in fewer changes to be made in the future.”

Having that big-picture view, and working within standards, can lead to more successful projects. “Having a clear set of company standards saves time on future projects,” Melville said. “It prevents you from having to re-invent the wheel every time. You can hit the ground running on new projects because you have a solid foundation in place.”

Jim Meyers is communications manager at Inductive Automation. Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media and Technology, mhoske@cfemedia.com.

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KEYWORDS: HMI design, SCADA design, HMI standards

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